Detailed overview of The Power of Habit, by Charles Duhigg

The New York Times investigative journalist Charles Duhigg’s The Power of Habit is a lively and engaging read that teaches you about the neurophysiology of habit formation through a series of page-turning anecdotes from various sectors of society. Split mainly into three sections dealing with the habits of individuals, of organizations, and then of society, Duhigg illustrates how the deeply-researched and well-understood “habit loop” (i.e. cue, routine, reward) is manifest (and subsequently modified) in a variety of interesting situations.

The Neurophysiology of Habit Formation: how habits are formed in the structures of the old brain

To a layperson in psychology such as myself, I was struck by the compelling nature of neurological research into habit formation. In the 1990s, MIT researchers studying mice discovered that habits are directly encoded into the basal ganglia, which are very old-brain structures close to the brain stem. As a habit becomes well-entrenched, a sort of neurological groove is carved into our brains which requires decreasing amounts of cognitive activity to deploy them. Evolutionarily, this helpfully frees up our brains to focus on more important things while performing repetitive or well-known tasks. However, with “bad” habits, this means that we can “check out” cognitively while deploying the habit. This may well explain why we find ourselves repeating our bad habits so mindlessly, ad nauseam. Unless you deliberately fight a habit by finding new routines, the pattern will unfold automatically without any conscious effort on our part.

Experiments on basal ganglia in mice have also shown that if you extinguish the habit by moving or changing the reward, the old habit will crop up again in its same place as soon as the reward is returned to its original place or position. Researcher Ann Graybiel explains:

Habits never really disappear. They’re encoded into the structures of our brain, and that’s a huge advantage for us, because it would be awful if we had to relearn how to drive after every vacation. The problem is that your brain can’t tell the difference between bad and good habits, and so if you have a bad one, it’s always lurking there, waiting for the right cues and rewards.

On the mechanism of craving

Early in the book, Duhigg also teaches us how cravings are created when the reward for a given habit’s cue is delayed or withheld entirely. By depositing a drop of blackberry juice on their tongues, rhesus monkeys in behavioural studies conducted by Wolfram Shultz at Cambridge in the 1990s were quickly trained to press a lever after certain shapes were displayed on a computer monitor. When delivery of the reward was delayed, however, the monkey’s brains would still light up after the cue was displayed—even before the lever was pressed. The brain anticipated the reward and pre-emptively reacted accordingly. Not surprisingly, these monkeys became angry and frustrated when the reward was permanently withheld, demonstrating how strongly and easily a craving is formed.

The conclusion from these studies was that habits create real neurological cravings. Furthermore, once a habit is fully engrained, as soon as the appropriate cue is perceived, a craving develops automatically. Duhigg reports that researchers at University of Michigan later wrote that particularly strong habits in alcoholics, smokers and overeaters produce addiction-like reactions so that “wanting evolves into obsessive craving” that can force our brains into autopilot, “even in the face of strong disincentives, including loss of reputation, job, home, and family.”